Measurement of naphthoxylactic and naphtoxyacetic acid in human plasma following propranolol administration.

A method for the quantitative determination of naphthoxylactic acid and naphthoxyacetic acid, two acidic metabolites of propranolol, in human plasma is described. Preliminary data from hypertensive patients receiving chronic propranolol therapy and from normal volunteers who took a single 80 mg oral propranolol dose revealed that naphthoxylactic acid plasma levels were 4 to 20 times that of propranolol whereas naphthoxyacetic acid levels were equivalent to or less than the plasma concentrations of propranolol.